I've owned a bunch of Fiio products and I can agree that companies certainly pick up a house sound. It is obvious to me that Fiio is going for a warm presentation, and I think that a lot of people prefer that. Fiio is great at listening to the market and giving people what they want and I think they have done a great job of that. I was a fan of it, but got tired of that warm sound as I prefer the analytical sound of the rest of my gear.
What I really love about iBasso is that they are dedicated to making a top notch player that sounds as neutral as possible. This is what I see and hear. I don't really notice any difference between FW updates at all, honestly, it has just sounded clean, clear, and true to the music at every step. I wish there were more companies with this outlook. Schiit is certainly there, and my Ascend Acoustics speakers are the most clean, clear, accurate, and honest speakers I've ever heard as well. I'm really glad that I could add a DAP to my gear that accomplishes the same goals.
It's actually pretty confusing to me to read all of the issues and talk of sound differences, and I'm sure it's insanely frustrating for iBasso to try to sift through it as well. I wish them the best of luck in nailing down all of these issues, especially before the DX200 is released.